Bulky or texturized yarns in which relatively straight and closely compacted filaments have been separated and convoluted by passing the unbulked yarn through an enclosed area of fluid turbulence are well known in the prior art. U.S. Pat. No. 2,783,609 discloses one such yarn and the apparatus for producing it. Bulky yarns of this type are characterized by the presence of large numbers of closed or crunodal loops which vary in size in accordance with the fluid pressure at the jet and the relative rates of which the yarn is fed to and withdrawn from the area of fluid turbulence or jet. Also bulky yarns having a core portion of substantially linear, closely grouped filaments and groups of dispersed filaments in successive regions along the outside surface of the core portion extending outwardly in elongated undulatory waves are well known in the prior art. U.S. Pat. No. 3,411,287 and No. 3,488,670 disclose such a yarn and the method and apparatus for producing it.
Also, composite bulked yarns having intermittent areas of increased texturization or bulkiness are well known in the art. U.S. Pat. No. 3,262,177 discloses a composite texturized yarn having primarily one degree of bulkiness over the entire length of the yarn with intermittent areas of increased texturization or bulkiness, known as slubs, intermittently located along the length of the yarn. Such a yarn is characterized by convolutions or closed loops that impart the bulkiness to the yarn. The yarn is texturized by passing the component yarns simultaneously through a zone of fluid turbulence or a jet. The slubs are induced intermittently into the yarn by increasing the speed of the feed rolls delivering at least one of the yarns to the jet or zone of fluid turbulence.